DESCRIPTION: Chlorine gas exposure occurs in occupational environments. Chlorine gas inhalation results in dose-dependent for acute and chronic pulmonary responses to chlorine exposure are unknown decrements in pulmonary function and respiratory tract irritation. The risk factors and controlling mechanisms. The specific aims of this study are to determine: (1) the effects of asthma with pre-existing airway hyper reactivity on the pulmonary function and airway reactivity and inflammation responses to chlorine; (2) the effects of chlorine concentration on the pulmonary function and airway reactivity and inflammation responses to chlorine concentration on the pulmonary function and airway reactivity and inflammation responses to chlorine; and (3) to assess the time dynamics of the pulmonary function and airway reactivity and inflammation responses to chlorine. It is hypothesized that both airway hyperactivity and higher chlorine concentration will result in larger changes in pulmonary function and airway reactivity and inflammation responses, and that these changes will have differential time courses following chlorine exposure. This study will use two controlled human exposure human exposure experiments, utilizing a single-blind, repeated-measures, and counter- balanced design. The two subject groups for both experiments will consist of 21 individuals with no airway hyperactivity, and 21 individuals with both asthma and airway hyperactivity. In Experiment One, subjects will be exposed for 15 min separately to each of: (1) chlorine at 0.4 ppm; (2) chlorine at 1.0 ppm; and (3) filtered air (Control). Pulmonary function and airway reactivity will be measured immediately pre-exposure and 1 and 20 h post-exposure. Airway inflammation, as determined by cellular and biochemical components from sputum-induction, will be measured 65h pre-exposure and 20 h post-exposure. In Experiments Two, subjects will be exposed for 15 min separately to each of: (1) chlorine (concentration determined from Experiment One); (2) filtered air (Control). Pulmonary function and airway reactivity will be measured immediately pre-exposure and at 3 and 72 h post-exposure. Sputum-induction will be performed 65h pre-exposure at 3 and 72 h post-exposure. The results of this study will provide information on a major irritant chemical relevant to occupational environments. Specially, the susceptibility of a large sub-population at increased risk, the dose-response effects, and the post-exposure time dynamics of the effects of chlorine gas will be determined.